264 lines
5.2 KiB
Markdown
264 lines
5.2 KiB
Markdown
UPDATE
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===========================
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描述
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-----------
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该语句用于修改表中的字段值。
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格式
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```javascript
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UPDATE [IGNORE] table_references
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SET update_asgn_list
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[WHERE where_condition]
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[ORDER BY order_list]
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[LIMIT row_count];
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table_references:
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tbl_name [PARTITION (partition_name,...)] [, ...]
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update_asgn_list:
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column_name = expr [, ...]
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order_list:
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column_name [ASC|DESC] [, column_name [ASC|DESC]...]
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```
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参数解释
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-------------
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| **参数** | **描述** |
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|------------------|-----------------------------|
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| IGNORE | 在 INSERT 语句执行过程中发生的错误将会被忽略。 |
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| table_references | 指定修改表名，多表修改时，表名直接'，'作为间隔。 |
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| where_condition | 指定过滤条件。 |
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| row_count | 限制的行数。 |
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| tbl_name | 插入表名。 |
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| partition_name | 插入表指定的分区名。 |
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| column_name | 列名。 |
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| column_name ASC | 按列名升序修改。 |
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| column_name DESC | 按列名降序修改。 |
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注意事项
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-------------
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不管是多表还是单表更新都不支持直接对子查询进行更新值操作，例如：`update (select * from t1) set c1 = 100;`
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示例
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-----------
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1. 创建示例表 t1 和 t2。
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```javascript
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OceanBase(admin@test)>create table t1(c1 int primary key, c2 int);
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Query OK, 0 rows affected (0.16 sec)
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OceanBase(admin@test)>select * from t1;
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+----+------+
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| c1 | c2 |
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+----+------+
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| 1 | 1 |
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| 2 | 2 |
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| 3 | 3 |
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| 4 | 4 |
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+----+------+
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4 rows in set (0.06 sec)
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OceanBase(admin@test)>create table t2(c1 int primary key, c2 int) partition by key(c1) partitions 4;
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Query OK, 0 rows affected (0.19 sec)
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OceanBase(admin@test)>select * from t2;
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+----+------+
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| c1 | c2 |
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+----+------+
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| 5 | 5 |
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| 1 | 1 |
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| 2 | 2 |
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| 3 | 3 |
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+----+------+
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4 rows in set (0.02 sec)
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```
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2. 将表 t1 中 "t1.c1=1" 对应的那一行数据的 c2 列值修改为 100。
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```javascript
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OceanBase(admin@test)>update t1 set t1.c2 = 100 where t1.c1 = 1;
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Query OK, 1 row affected (0.02 sec)
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Rows matched: 1 Changed: 1 Warnings: 0
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OceanBase(admin@test)>select * from t1;
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+----+------+
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| c1 | c2 |
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+----+------+
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| 1 | 100 |
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| 2 | 2 |
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| 3 | 3 |
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| 4 | 4 |
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+----+------+
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4 rows in set (0.01 sec)
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```
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3. 将表 t1 中按照 c2 列排序的前两行数据的 c2 列值修改为 100。
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```javascript
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OceanBase(admin@test)>update t1 set t1.c2 = 100 order by c2 limit 2;
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Query OK, 2 rows affected (0.02 sec)
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Rows matched: 2 Changed: 2 Warnings: 0
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OceanBase(admin@test)>select * from t1;
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+----+------+
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| c1 | c2 |
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+----+------+
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| 1 | 100 |
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| 2 | 100 |
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| 3 | 3 |
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| 4 | 4 |
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+----+------+
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4 rows in set (0.01 sec)
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```
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4. 将表 t2 中 p2 分区的数据中 "t2.c1 \> 2" 的对应行数据的 c2 列值修改为 100。
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```javascript
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OceanBase(admin@test)>update t2 partition(p2) set t2.c2 = 100 where t2.c1 > 2;
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Query OK, 1 row affected (0.02 sec)
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Rows matched: 1 Changed: 1 Warnings: 0
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OceanBase(admin@test)>select * from t2;
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+----+------+
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| c1 | c2 |
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+----+------+
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| 5 | 5 |
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| 1 | 1 |
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| 2 | 2 |
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| 3 | 100 |
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+----+------+
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4 rows in set (0.06 sec)
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```
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5. 修改多个表。将 t1 表和 t2 表中满足 "t1.c1 = t2.c1" 对应行的数据 t1 表中的 c2 列值修改为 100，t2 表中的 c2 列值修改为 200。
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```javascript
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OceanBase(admin@test)>update t1,t2 set t1.c2 = 100, t2.c2 = 200 where t1.c2 = t2.c2;
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Query OK, 6 rows affected (0.03 sec)
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Rows matched: 6 Changed: 6 Warnings: 0
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OceanBase(admin@test)>select * from t1;
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+----+------+
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| c1 | c2 |
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+----+------+
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| 1 | 100 |
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| 2 | 100 |
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| 3 | 100 |
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| 4 | 4 |
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+----+------+
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4 rows in set (0.00 sec)
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OceanBase(admin@test)>select * from t2;
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+----+------+
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| c1 | c2 |
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+----+------+
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| 5 | 5 |
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| 1 | 200 |
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| 2 | 200 |
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| 3 | 200 |
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+----+------+
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4 rows in set (0.01 sec)
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```
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6. 修改多个表。修改 t1 表和 t2 表的p2分区中满足 "t1.c1 = t2.c1" 对应行的数据 t1 表中的 c2 列值修改为 100，t2 表中的 c2 列值修改为 200。
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```javascript
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OceanBase(admin@test)>update t1,t2 partition(p2) set t1.c2 = 100, t2.c2 = 200 where t1.c2 = t2.c2;
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Query OK, 6 rows affected (0.02 sec)
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Rows matched: 6 Changed: 6 Warnings: 0
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OceanBase(admin@test)>select * from t1;
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+----+------+
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| c1 | c2 |
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+----+------+
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| 1 | 100 |
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| 2 | 100 |
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| 3 | 100 |
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| 4 | 4 |
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+----+------+
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4 rows in set (0.01 sec)
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OceanBase(admin@test)>select * from t2;
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+----+------+
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| c1 | c2 |
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+----+------+
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| 5 | 5 |
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| 1 | 200 |
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| 2 | 200 |
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| 3 | 200 |
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+----+------+
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4 rows in set (0.01 sec)
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```
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7. 对可更新视图 v 进行更新值。
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```javascript
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OceanBase(admin@test)>create view v as select * from t1;
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Query OK, 0 rows affected (0.07 sec)
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OceanBase(admin@test)>update v set v.c2 = 100 where v.c1 = 1;
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Query OK, 1 row affected (0.02 sec)
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Rows matched: 1 Changed: 1 Warnings: 0
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OceanBase(admin@test)>select * from v;
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+----+------+
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| c1 | c2 |
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+----+------+
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| 1 | 100 |
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| 2 | 2 |
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| 3 | 3 |
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| 4 | 4 |
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+----+------+
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4 rows in set (0.01 sec)
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```
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